The present invention relates generally to mechanisms which allow for length adjustment of shafts or rods, and more particularly to mechanisms using a rheological fluid to perform the releasing and locking functions. Such mechanisms can be used in various applications, including headrests, steering columns and seats.
Various types of length adjustable and torque transmittable devices are generally known in the art to be utilized in a range of applications. These devices, while allowing for length adjustment and continued torque transmittal, tend to be complex in their designs. This complexity is a result of the various mechanical features required to perform the locking and releasing functions.
In order to reduce the complexity of such mechanisms, it is an object of the present invention to provide an improved method for adjusting the length of shafts or rods, specifically those required to transmit torque. To achieve this, the present invention utilizes rheological fluid in combination with a piston-like device. The fluid can be switched between two phases, liquid and solid, by introduction of an electric or magnetic field. The solid phase effectively locks the device in position while the liquid phase allows for easy adjustment. By utilizing this invention, the mechanical latching devices, springs and racks of prior art inventions are easily replaced, reducing overall complexity. This allows for fewer parts, ease in production and ease in maintenance.
Such a device can be used in various applications. One such application is the position adjustment of a steering wheel. The variable length shaft system can be integrated into the steering column allowing for positional adjustment.
Two other applications include methods for adjusting the headrest and seatback of seats. In the headrest application, the variable length shaft system can be introduced to perform two main functions: connect the headrest to the seatback and allow for vertical adjustment of the headrest. The seatback application would use the variable length shaft system simply as a locking device, which allows a person to adjust the seatback then lock it in position.
Another application of the variable length shaft system would be for use with a door or a rear hatch of a vehicle. Integrating this system with a door could allow the door to be opened to an infinite number of positions and then can be locked in that position. Another application of the present invention is for use in an anti-whiplash headrest. This application would integrate the variable length shaft system into a headrest which additionally houses a spring loaded pivotal headrest mount. In the event of an accident the variable length shaft system would be deactivated, allowing the headrest to automatically spring forward, reducing the possibility of neck injury.